pub fn dp_rec_mc(amount: u32) -> u32 {
    //1, 2, 5, 10, 20, 30, 50, 100 yuan
    let currency_types: Vec<u32> = vec![1, 2, 5, 10, 20, 30, 50, 100];
    let mut amount = amount;
    let mut bill_count = 0;
    for v in currency_types.iter().rev() {
        loop {
            if amount >= *v {
                amount -= *v;
                bill_count += 1;
            } else {
                break
            }
        }
    }
    // TODO: 这里写逻辑
    bill_count
}
